Sappho

A published hardiness zone describes a whole county. It has nothing to say about the four metres between the foot of a sunlit wall and the bottom of the steps, which is where the cold actually sits, and that is the distance most tender plants are lost over. Sappho works at that scale. It treats a garden as a set of distinct spots and gives each one its own night minimum, computed rather than looked up. You photograph a corner of the plot and drop numbered pins on what is in the frame: the masonry, the paving, the water, the turf, the glass, the gap in the canopy. Each pin carries its surface material, its height and its distance from the spot, and from those Sappho derives the minimum from six named terms — wall mass, sky view under a canopy, cold-air fall and pooling, exposure, the buffer of a water body, and paving mass. Twelve spots come already surveyed, so the method is visible before you survey anything of your own. The point of a figure is what it decides. Every tender subject is plotted against every spot as a margin in degrees, and Sappho names the term that governs each verdict, so you learn 📖 whether a plant holds on the wall's strength or whether the canopy is doing all the work. A nine-item key covers the ways a good spot goes wrong ❌ — the frost hollow, the wind funnel, the gutter drip, the salt crust — each with the penalty it carries and how to put it right. Out of all that Sappho orders a twelve-month 🗓️ protection programme: which cover, on which plant, in which spot, and the window it belongs in. Every figure is arithmetic done ✅ on the device 📱. There is no weather 🌤️ feed, no zone lookup, and no connection of any kind.